Plastics Electronics. Strength of thin glass foils for electronic encapsulation

Transcription

1 Plastics Electronics Strength of thin glass foils for electronic encapsulation

2 SCHOTT AG, Ultra-thin glass Kurt Nattermann, Thomas Rossmeier, Markus Heiss, Clemens Ottermann Plastics Electronics Conference Oct. 2013

3 Ultra-thin and flexible glass from SCHOTT AG is available as cut-to-size sheet and on roll Glass Sheet Glass roll Nominal thickness: 25, 50, 70, 100 micron Width up to 600 mm Cut-to-size format Nominal thickness: 50 micron Width up to 600 mm Standard length on roll: 10 m Several hundred meters of various glass thicknesses successfully rolled and unrolled Rolls already shipped to customers for R2R process trials

4 Properties of Ultra-thin glass (AF32 eco) alcaline content: no Young s modulus: E = 74.8 GPa, ν = density: ρ = 2.43 g/cm 3 coeff. of therm. expansion: α = /K therm. conductivity: dielectric const. (@ 1MHz): ε = 5.1 loss tangent (@ 20 C): λ = 1.04 W/(m K) δ = /MHz bulk resistivity (< 200 C ): ρ >> Ω mm 2 /m refractive index: n D = lum. transmittance (0.5mm): T = 91.9% diffusivity (@ 20 C, 30µm): O 2 : D << 10-2 cm 3 /(m 2 24h) H 2 O: D << 10-5 g/(m 2 24h) (at least 3 orders lower than typical values of plastics!)

5 Specialized technology development in progress to complement the processing capabilities of SCHOTT Product/Technology Requirement Potential Applications High Quality Cutting Carrier systems TGV drilling Lamination Coating High Index Glass Edge Strength Enhancement Sheets and rolls of glass OLED Lighting Interposer Window laminates Thin Film Batteries Sensors Capacitors Technology competencies in expansion to address the specialized needs of applications

6 Various application fields are possible due to high performance ultra-thin glass OLED Displays OLED / Lighting Thin Film Solar Cells/OPV Source: AndroidPIT, Source: LEDs Magazine by Laura Peters, Source: Sun Flare Systems Thin Film Batteries Thin Film Capacitors Touch Sensors Source: KAIST, Source: SeanBreeden.com Source: Solid State Technology Printed Circuits RFID Electronic Paper Source: Printed s.r.o. Source: Fujitsu Source: TabTimes by Doug Drinkwater,

7 focus of this talk: strength (= fracture probability ) and reliability (i.e. expected lifetime ) of (thin) glass sheets

8 Strength of glass rupture loads of ductile vs. brittle materials: F ductile material brittle material SttR9150 load [a.u.] simply speaking: ductile materials flow, before they break brittle materials break, before they flow weakening surface flaws are important the statistics of flaws have a dominant effect

9 Lifetime Distributions common lifetime statistics: log-normal-distribution: log-weibull-distribution: Poisson-distribution: F t(t) = 1 ln(t) µ 1 erf σ F t(t) = ( ln(t) ) 1 exp m µ MTFF, MTBF = 1 λ ( λ: failure rate) determined from: focus in this talk field observations: (i.e. observed lifetimes ) accelerated lifetime testing: ( ALT, HALT ) strength testing: (dynamic and static methods) F t(t) ( ) F t, σ F (t, σ) t excess t strength ( σ) ( ) F F t t

10 Strength- & lifetime-testing methods from strength to lifetime with static load with dynamic load σ 3 Prüfung σ math. Modell σ 2 σ 1 math. Modell σ nom Extrapolation σ nom "start" t [a.u.] RelMb10c "start" t [a.u.] RelMb10d simple procedure extremely time consumptive fast, fracture always occurs ageing is disregarded

11 Stress in a deformed glass foils example: uniaxial bend small specimen: 1 st principal stress at top face (in MPa): glass thickness: t = 0.05mm quadratic device size: mm 2 bend with R = 30 mm glass AF32 stresses can be found in text books (... thin shells) faces: edges: E t σ face = 2 1 2R 66 M P a ν t σ edge = E 61MPa 2R

12 Surface Strength Testing ball-on-clamped-ring tests: F glass supported typ. data: sphere: R = 50 mm (steel) ring: R i = 35 mm (PMMA) glass: = 100 mm, t = µm by a ring and loaded by a sphere FEA-results, 50µm AF32, radial stress: F [N] σ [MPa] nearly homogeneous (and isotropic) stress within contact circle contact radius up to 10 mm and stress level up to GPa feasible r [mm] 0 0

13 F assessment of surface data from strength to lifetime MPa st : tested area large device A test = 80 mm 2 A dev = 625 mm 2 (fract. prob. increases by 1 order) σ [MPa] nd : dyn. tests permanent load σ i math.model t i F 0.5 fracture probability within 1 y: < 1% either an article will break very fast or never t lifetime [years] 10 14

14 Edge Strength Testing two-point-bend tests: R min specimen σ() 1 R( ) flat arrangement of specimens only inhomogeneous stress (only a short part, length a few mm, are tested) both (left and right) edges are loaded note: strength may be different for top and bottom face!

15 assessment of edge data from strength to lifetime st : short 2pb-edges long edges L test = 8 mm L dev = 2 25 mm F σ [MPa] 2 nd : dyn. tests permanent load σ i math.model fracture probability within 1 y: < 1% either an article will break very fast or never t i F day month t lifetime [years]

16 résumé: SCHOTT is a supplier for ultra-thin (thickness down to 30 microns!) glass foils (sheets and rolls) suitable for superior tight encapsulation of various electronic components. Physical und chemical properties of glasses can be tailored with respect to the demand of customers. SCHOTT can support customers by the development of glass handling and processing (e.g. cutting, separation ) methods. Several methods are established at SCHOTT for calculating the lifetime of articles during the whole lifecycle of an article from data obtained in fast tests. A reliable lifetime estimation requires information about initial strength (e.g. flaw statistics at shipment) strength diminution mechanisms in various environments handling/processing of articles by customers/users.

17 Thank You for Your Attention!